Saturated phase shift circuit



Oct. 17, 1967 H. H. HOGE SATURATED PHASE SHIFT CIRCUIT Filed March 25,1965 FIG. 2

IN VENTOR HE/VR/ H065 BY (Zaxa/ W FIG. 3

ATTORNEY United States Patent 3,348,134 SATURATED PHASE SHIFT CIRCUITHenri H. Hoge, Baltimore, Md., assignor, by mesne assignments, to theUnited States of America as represented by the ecretary of the NavyFiled Mar. 25, 1965, Ser. No. 442,834 4 Claims. (Cl. 323-126) Thepresent invention relates generally to a phase shift circuit and moreparticularly to a phase shift circuit utilizing saturable reactors.

When utilizing multi-phase power supplies, it is necessary that one ormore of the outputs be adjusted in phase with respect to a standard.Generally, with the increased use of solid state switching devicesfollowing such a power supply, a square wave is utilized for switchingin such an operation. Particularly when silicon controlled rectifiersare utilized, it is required that the signal drive to such elements becontinuous throughout the half cycle that such elements are in their oncondition.

Conventional phase shifters do not lend themselves to the type ofoperation described above. This is especially true with the conventionalR-C type phase shift network due to losses associated therewith and thevariable reactive loads to which the signal from the phase shift circuitis applied.

Further, prior art devices have been contemplated utilizing a squareloop magnetic core to delay or phase shift an input waveform byemploying the blocking characteristic of a core. These devices, however,also fall short of a complete solution to the problem mentionedhereinabove in that they do not provide drive for a complete detectedhalf cycle of operation, without utilization of additional elementsproviding feedback to complete the drive cycle.

The present invention provides an inexpensive and uncomplicated solutionto this problem, utilizing a low impedance square loop core in a novelarrangement to obtain a complete half cycle phase shifted drive signalwithout the use of auxiliary feedback circuitry.

An object of the present invention is the provision of a reliable phaseshifter.

Yet another object of the present invention is the provision of a phaseshifter which provides a complete half cycle drive signal.

Still another object of the invention is to provide a phase shiftedcomplete half cycle drive signal without the use of complicated feedbackcircuitry.

Other objects and features of the present invention will become apparentupon consideration of the following description when considered inconjunction with the appended claims and accompanying figures ofdrawing, wherein:

FIG. 1 illustrates a schematic drawing of an embodiment of theinvention;

FIG. 2 depicts waveforms at various points on the embodiment of FIG. 1when a square Wave input is applied thereto; and

FIG. 3 depicts waveforms at various points on the embodiment of FIG. 1when a sinusoidal waveform input is applied thereto.

Turning now to FIG. 1, there is shown an input transformer 11, thesecondary Winding 12 of which is connected on either end to coils 13 and14, respectively, which coils are wound about a square loop magneticcore 15. Coils or windings 13 and 14 are wound about the core in such adirection that a positive current from the transformer to either coilwill induce a clockwise flux pattern in the core 15. The other end ofcoils 13 and 14 are connected to the anode of diodes 16 and 17,respectively, both of the cathodes of these diodes are tied to ajunction point 18. Between the connection of coil 13 and diode 16, oneend of a resistor 19 is connected, the other end of which is connectedto the junction formed by the secondary 12 and coil 14. A furtherresistor 21 is connected on one end to the junction 18 and on the otherend to the junction formed by the secondary 12 and coil 14.

FIG. 2, waveform a, illustrates the waveform appearing at point a of thesecondary 12 of transformer 11 when a square wave input signal isapplied to the transformer. Waveforms b and c are the waveforms at theoutput of coils 13 and 14, respectively, induced by waveform a. Assumingthe core to be in negative saturation at the time t waveform ainstantaneously changes to a positive value. Due to the volt-secondcharacteristics of the core, no signal appears at point b until the coreflips from negative to positive saturation. This occurs at time t Attime t the square wave a again changes instantaneously to a negativevalue causing the core to flip to the region of negative saturation attime t, which in turn causes the negative waveform shown in FIG. 2b,between times t and t At time t the cycle commences again.

While the waveforms at point b appear as described above, the coil 14induces the waveforms at point c as shown in FIG. 20, since coil 14 isconnected to the other side of the secondary winding 12 from that ofcoil 13. As the square wave a changes polarity, instantaneously, thewaveforms appearing at point e are generated and appear at alternatetime slots from those of FIG. 2b.

The diodes 16 and 17 only allow currents to flow therethrough that arepositive. Thus, the detected and combined output appearing at d, oracross resistor 21, is a combination of the positive portions of thewaveforms b and c.

In practice, as seen in FIG. 2d, there is a slight switching notch inthe waveshape. This is so slight that it may be neglected, and theoutput signal constitutes a phase shifted signal which is continuous fora half cycle for all practical applications.

The amount of delay or phase shift may be controlled by choosing a corewith appropriate volt-second characteristics; that is, with anappropriate cross-section, and by the number of turns of coils 13 and14. Obviously, other circuit parameters are carefully selected to obtainthe correct output signal.

As shown in FIG. 3, a sinusoidal input signal applied to the transformer11 results in the waveform of FIG. 3a as an input to the device. FIG. 3dillustrates that a phase shifted signal results.

The principle of operation is the same as that described above withrespect to FIG. 2.

Thus, a device has been fully disclosed which provides a complete halfcycle phase shifted output signal.

Obviously many modifications and variations of the present invention arepossible in the light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims in the inventionmay be practiced otherwise than as specifically described.

What is claimed is:

l. A half cycle phase shift circuit for shifting the positive portiononly of an alternating Voltage and attenuating the negative portionthereof comprising:

a magnetic core characterized by binary stages of saturation;

a first and a second coil wound about said core wherein said first coilsets said magnetic core to one of its binary stages of saturation andsaid second coil resets said magnetic core to its other binary stage ofsaturation;

means for applying an alternating voltage to said coils;

and

first and second unidirectional current devices each having twoterminals, said unidirectional current devices being connected to saidfirst and second coils,

respectively, at one terminal and in common together at the otherterminal; and an output resistor coupled to said common connection ofsaid first and second unidirectional current devices.

2. The circuit of claim 1 wherein said first and second coils are at anyone instant referred to voltages of opposite sense one relative to theother.

3. The device of claim 1 wherein said magnetic core is ofthe squarehysteresis loop type.

4. The device of claim 2 wherein said unidirectional current devices arediodes.

References Cited 5 UNITED STATES PATENTS 3,026,504 3/1962 Aurand et a1323-126 X 3,031,610 4/1962 Hamilton 323-8912 3,210,651 10/1965 Runyan323l08 10 JOHN F. COUCH, Primary Examiner.

A. D. PELLINEN, Assistant Examiner.

1. A HALF CYCLE PHASE SHIFT CIRCUIT FOR SHIFTING THE POSITIVE PORTIONONLY OF AN ALTERNATING VOLTAGE AND ATTENUATING THE NEGATIVE PORTIONTHEREOF COMPRISING: A MAGNETIC CORE CHARACTERIZED BY BINARY STAGES OFSATURATION; A FIRST AND A SECOND COIL WOUND ABOUT SAID CORE WHEREIN SAIDFIRST COIL SETS SAID MAGNETIC CORE TO ONE OF ITS BINARY STAGES OFSATURATION AND SAID SECOND COIL RESETS SAID MAGNETIC CORE TO ITS OTHERBINARY STAGE OF SATURATION; MEANS FOR APPLYING AN ALTERNATING VOLTAGE TOSAID COILS; AND FIRST AND SECOND UNIDIRECTIONAL CURRENT DEVICES EACHHAVING TWO TERMINALS, SAID UNIDIRECTIONAL CURRENT DEVICES BEINGCONNECTED TO SAID FIRST AND SECOND COILS, RESPECTIVELY, AT ONE TERMINALAND IN COMMON TOGETHER AT THE OTHER TERMINAL AND AN OUTPUT RESISTORCOUPLED TO SAID COMMON CONNECTION OF SAID FIRST AND SECONDUNIDIRECTIONAL CURRENT DEVICES.